As image pickup modules, various types of compact digital cameras, compact digital video units, and the like have been developed each of which houses a solid-state image sensing device such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor). In particular, portable terminals such as portable information terminals and portable phones have spread in recent years. Accordingly, image pickup modules to be provided in the portable terminals are required to be small in size, low in height and high in resolving power.
A technique for increasing a resolving power of an image pickup lens to be provided in such an image pickup module, and reducing a size and a height of the image pickup lens attracts attention, as a technique for satisfying such requirements. As one example of such a technique, Patent Literatures 1 through 4 disclose respective image pickup lenses having the following arrangements.
Each of the image pickup lenses disclosed in Patent Literatures 1 through 4 has an aperture stop and a single lens which are provided in this order from an object (subject) side to an image surface (image forming surface) side. The single lens is one well-known meniscus lens whose concave surface faces the object side.
Such image pickup lenses are required to have a wide angle at which an image can be formed, i.e., a wide angle of view, in order that a high resolving power may be realized at an edge of a formed image and in the vicinity thereof (hereinafter, referred to as “a periphery of a formed image”). In order to realize an image pickup lens having a wide angle of view, it is effective to arrange the image pickup lens so that its single lens may be sufficiently thin, with respect to a center thickness thereof, at an end (hereinafter, referred to as “lateral side of the single lens”) of the effective aperture of the single lens which end is located along a direction normal to an optical axis of the image pickup lens.
The image pickup lens disclosed in Patent Literature 4 is arranged so as to satisfy the following formula (A). This makes it possible to reduce a thickness of a lateral side of its single lens with respect to a center thickness of the single lens.0.5≦d1′/d1≦0.9  (A)where: d1′ is a thickness of that thinnest portion of the single lens which is located in an area including at least one optical surface of the single lens; and d1 is a center thickness of the single lens.
In addition, the image pickup lens disclosed in Patent Literature 4 is arranged so as to satisfy the following formula (B). This makes it possible to realize an image pickup lens having a wide angle of view.0.6≦Y′/fl  (B)where: fl is a focal length of the whole lens system; and Y′ is the maximum image height.